chore: activate clippy::manual_let_else lint

Refactor let else usage to align w/ idiomatic usage of Rust by activating `clippy::manual_let_else` lint, and resolving all the warning messages.

Resolves: libp2p#4741.

Pull-Request: libp2p#4770.

src/behaviour/as_client.rs

@@ -278,13 +278,9 @@ impl<'a> AsClient<'a> {
             tracing::debug!("Outbound dial-back request aborted: No dial-back addresses");
             return Err(OutboundProbeError::NoAddresses);
         }
-        let server = match self.random_server() {
-            Some(s) => s,
-            None => {
-                tracing::debug!("Outbound dial-back request aborted: No qualified server");
-                return Err(OutboundProbeError::NoServer);
-            }
-        };
+
+        let server = self.random_server().ok_or(OutboundProbeError::NoServer)?;
+
         let request_id = self.inner.send_request(
             &server,
             DialRequest {
@@ -301,11 +297,8 @@ impl<'a> AsClient<'a> {
     // Set the delay to the next probe based on the time of our last probe
     // and the specified delay.
     fn schedule_next_probe(&mut self, delay: Duration) {
-        let last_probe_instant = match self.last_probe {
-            Some(instant) => instant,
-            None => {
-                return;
-            }
+        let Some(last_probe_instant) = self.last_probe else {
+            return;
         };
         let schedule_next = *last_probe_instant + delay;
         self.schedule_probe

src/behaviour/as_server.rs

@@ -326,13 +326,13 @@ impl<'a> AsServer<'a> {
         demanded: Vec<Multiaddr>,
         observed_remote_at: &Multiaddr,
     ) -> Vec<Multiaddr> {
-        let observed_ip = match observed_remote_at
+        let Some(observed_ip) = observed_remote_at
             .into_iter()
             .find(|p| matches!(p, Protocol::Ip4(_) | Protocol::Ip6(_)))
-        {
-            Some(ip) => ip,
-            None => return Vec::new(),
+        else {
+            return Vec::new();
         };
+
         let mut distinct = HashSet::new();
         demanded
             .into_iter()

src/protocol.rs

@@ -119,22 +119,18 @@ impl DialRequest {
         if msg.type_pb != Some(proto::MessageType::DIAL) {
             return Err(io::Error::new(io::ErrorKind::InvalidData, "invalid type"));
         }
-        let (peer_id, addrs) = if let Some(proto::Dial {
-            peer:
-                Some(proto::PeerInfo {
-                    id: Some(peer_id),
-                    addrs,
-                }),
-        }) = msg.dial
-        {
-            (peer_id, addrs)
-        } else {
-            tracing::debug!("Received malformed dial message");
-            return Err(io::Error::new(
-                io::ErrorKind::InvalidData,
-                "invalid dial message",
-            ));
-        };
+
+        let peer_id_result = msg.dial.and_then(|dial| {
+            dial.peer.and_then(|peer_info| {
+                let Some(peer_id) = peer_info.id else {
+                    return None;
+                };
+                Some((peer_id, peer_info.addrs))
+            })
+        });
+
+        let (peer_id, addrs) = peer_id_result
+            .ok_or_else(|| io::Error::new(io::ErrorKind::InvalidData, "invalid dial message"))?;
 
         let peer_id = {
             PeerId::try_from(peer_id.to_vec())